Vmxm reprocessing patch

[amyjaynethompson]

This PR fixes two small bugs VMXm found when using multiplex_filtering.

1. Their requested default image batch size wasn't being used (this was due to using '-' instead of '_' in the pydantic model). This has now been fixed by removing alias as not needed.
2. The ISPyB query was grabbing all original job parameters - however instead of overwriting new ones, it duplicated them. This was causing the multiplex_filtering pipeline to crash. This has been fixed by checking for which parameters from the original job had been declared in the reprocessing and removing those.